1. Field of the Invention
The present invention relates to a wheel and a method of manufacturing the same.
2. Description of the Related Art
One-piece type wheels which are integrally molded by casting, two-piece type wheels with a construction that is split into two parts, i. e., a rim and a disk, and three-piece type wheels with a construction that is split into three parts, i. e., an inner rim, and outer rim and a disk, are widely used as vehicle wheels that consist of light alloys such as aluminum alloys or the like.
In the case of two-piece type wheels and three-piece type wheels, wheels in which the disk is manufactured by casting or forging, and the rims are constructed using rolled metal plates have been adapted for practical use. Rims that are used in such cases include products in which band form rolled metal plates are rolled up into a cylindrical shape, both ends are welded, and the produced is molded into a desired shape by spinning, and products in which circular plate form rolled metal plates are press-molded into a cylindrical shape with a bottom, the bottom part is cut away, thus forming a cylindrical molded product, and this product is molded into a desired shape by spinning.
Furthermore, in the abovementioned vehicle wheels, in order to lock the inner circumferential edge part of the tire, hump parts that protrude outward are disposed circumferentially in the vicinity of both end parts of the rim, and rim flange parts that extend outward at an inclination in the radial direction are formed on both end parts of the rim (for example, see Japanese Patent Application Laid-Open No. 2003-236638). Furthermore, wheels in which at least the rim flange part on the design surface side is constructed with an increased thickness, folding this part back or curling this part into a cylindrical shape so that the strength and rigidity are increased, have also been adapted for practical use (for example, see Japanese Patent Application Laid-Open No. 2003-236638 and Japanese Patent Application Laid-Open No. 2003-236636).
Meanwhile, the requirements of users with respect to the design of wheels have become more diversified with each passing year, so that two-piece type wheels or three-piece type wheels that are superior in terms of productivity in the case of the manufacture of small amounts of diverse types have recently become more popular than one-piece type wheels that are superior in terms of mass production characteristics.